1. Field of the Invention
The present invention relates to a photomask and to a method of manufacturing a photomask, and more particularly to a photomask with reduced variation in light intensity caused by defocusing, enabling the achievement of a highly accurate micropattern, and a method of manufacturing such a photomask.
2. Description of the Related Art
Photomasks in the past were, for example, as shown in FIGS. 3 (a) and (b).
FIG. 3 (a) shows the first example of a prior art photomask, for the case of using an isolated residual pattern 11 in combination with positive photoresist, this photoresist being used to obtain a prescribed pattern. FIG. 3 (b) shows the case in which auxiliary patterns 12 are provided on both sides of the isolated residual pattern 11, separated therefrom by a prescribed spacing.
FIG. 3 (c) is a graph presenting a plot of the variation in light intensity on the photoresist for the case of using the isolated residual pattern 11, obtained with a defocusing step of 0.2 xcexcm, the dotted lines indicating the case of forming a pattern of 0.2 xcexcm width onto the resist, this showing how, with defocusing, there is a great change in the light intensity in the region in which the pattern is formed, so that defocusing results in the pattern becoming narrow.
In the case of using the isolated residual pattern shown in FIG. 3 (a), therefore, it is possible to obtain a depth of focus of only approximately 0.7 xcexcm, and even in the case of FIG. 3 (b), in which the method used is that of providing auxiliary patterns, it is only possible to obtain a depth of focus of 1.0 xcexcm.
In the case of FIG. 3 (b), to prevent resolution of the auxiliary pattern 12, it is necessary to make the width w of the auxiliary pattern 12 small and, for this reason, there is the problem of difficulty in fabricating the mask.
Known photomask is such as described, for example, in Japanese Unexamined Patent Publication (KOKAI) No.8-54727, but this photomask does not solve the above-described problem.
Accordingly, it is an object of the present invention to improve on the above-noted drawback of the prior art, and in particular to provide a photomask that reduces the variation in light intensity caused by defocusing, and enables the achievement of a highly accurate micropattern, and a method of manufacturing this photomask.
In order to achieve the above-noted object, the present invention adopts the following basic technical constitution.
Specifically, in the first aspect of a photomask according to the present invention, a translucent film is disposed on both sides of the isolated residual pattern, with a space pattern therebetween.
In a second aspect of the present invention, the width of the space pattern is approximately equal to the line width of the above-noted isolated residual pattern.
In the third aspect of the present invention, the transmissivity of the translucent film is in the range from 10% to 60%.
In the fourth aspect of the present invention, the translucent film does not invert the phase.
In the fifth aspect of the present invention, the width of the translucent film is at least the width of the isolated residual pattern.
In the first aspect of a method of manufacturing a photomask according to the present invention, an isolated residual pattern is formed onto the photomask, and a non-phase-inverting translucent film is placed on both sides of this isolated residual film, with a space pattern therebetween having a width that is approximately the same width as the isolated residual pattern, thereby reducing the variation in light intensity caused by defocusing.
In the second aspect of the above-noted method of manufacturing a photomask according to the present invention, the transmissivity of the translucent film is in the range from 10% to 60%.
A photomask according to the present invention has an isolated residual pattern formed onto a photomask, and has a translucent film formed on both sides of this isolated residual pattern, with a space pattern therebetween that has a width that is approximately equal to that of the isolated residual pattern. By adopting this configuration, even in the case of defocusing, the pattern that is formed onto the resist does not become narrower.
Furthermore, because a difficult-to-fabricate auxiliary pattern is not used, manufacturing is facilitated.